Some display panel techniques such as liquid crystal displays (LCD) require backlight. The backlight in large screens such as computer monitors and television sets is typically produced by arranging light sources such as light emitting diodes (LEDs) around a relatively thick planar light guide made of clear plastics. The light guide plate scatters through its surface light towards the LCD. The light is further diffused by an stack of light diffusing and prism foils. This technique is very common and can produce very even illumination of the LCD. However, a fair proportion of illuminating light radiated by the LEDs is lost in numerous reflections and refractions between the LEDs and the LCD. This results in increased illumination demand for the LEDs as well as heat dissipation, which may further contribute to accelerating aging of various components of the LCD device. The losses of illumination power also result in increased power consumption and in battery operated devices in reduced battery life in comparison to the ideal case in which all the light radiated by the LEDs could actually be used for backlighting.